The Taiwanese Patent No. 82200455 discloses a motorcycle disk brake lock, which comprises a rectangular lock body provided with a slot dimensioned to receive therein a motorcycle disk brake. The motorcycle disk brake is then arrested by a lock bolt which is put horizontally through one heat-radiating hole of the disk brake shoe, thereby incapacitating the motorcycle. Such a prior art motorcycle disk brake lock as described above is defective in design in that the lock body of the disk brake lock can fasten only the outer edge of the disk brake shoe if the distance between the lock bolt and the slot is too small, and that the inner portion of the lock body can touch the wheel hub of the motorcycle wheel to prevent the lock bolt to be put through the heat-radiating hole of the disk brake shoe if the distance between the lock bolt and the slot is too great. The similar situations as described above can also take place if the outer diameter of the disk brake shoe is too small.